Effect of particle state and coating microstructure on the adhesive strength of HVOF sprayed nickelbased alloy coatings

摘要

Nickel-based self-fluxing alloy (such as NiCrBSi) coatings were deposited using High Velocity Oxygen-Fuel (HVOF) spray process under different spray parameters with two powders of different particle sizes. The adhesive strength of coating was estimated according to ASTM C633-79. The coating microstructure and the tensile fractured cross sectional morphology were examined with optical microscope and Scanning Electron Microscopes. It is found that the molten state of sprayed particles has significant effect on the adhesive strength of HVOF sprayed NiCrBSi coating. The significant melting of sprayed particle does not contribute to increase in the adhesion of HVOF metallic coating. On the other hand, the coating deposited with large powder presents dense microstructure while substantially partially melted particles yield an adhesive strength of over 76 MPa, which is doubled compared with the coating deposited with completely molten particles.